Technical Field
The present invention relates to a system for producing reinforcing cages for wind turbine tower segments, wherein a reinforcing cage has in each case substantially horizontally oriented ring segments and substantially vertically oriented stiffening elements.
Description of the Related Art
Towers such as those which are used, inter alia, for wind turbines often have a wall made from concrete or reinforced concrete. In particular in the case of dynamically loaded towers, which applies to the majority of towers owing to the effect of the wind, stiffening structures, so-called reinforcing cages, are additionally provided inside the tower wall in order to improve stability. A tower hereby has a segmental structure, i.e., a tower is composed of multiple superposed ring-shaped tower segments.
In the production of such tower segments, the reinforcing cage is first produced and concrete is then poured into formwork provided for this purpose and left to set.
In known devices for producing reinforcing cages for tower segments, a support structure is provided which holds a plurality of bars, so-called rakes. These bars each have holders for holding reinforcing steel wire, wherein the reinforcing steel is passed around the support structure or the support structure is set in rotation in order to form ring elements. These ring elements are connected to bracket-like (steel) stiffening elements which extend substantially perpendicularly to the rings or substantially vertically, as a result of which a grid-like reinforcing cage is formed.
The reinforcing steel wire is either passed around a stationary support structure in a circular motion or, which is preferable, is situated in a stationary feed unit and is pulled out of the holder by the support structure which can be driven in rotation and is applied around the support structure owing to the rotational motion of the latter. During the whole time, the shape of the ring-shaped steel strands is stabilized by the support structure and the bars by means of multiple spokes which extend between the support structure and the bars. In order to remove the reinforcing cages from the device, in known systems the spokes must each be removed or the stabilizing bars are unhooked individually and manually from the finished cage.
Depending on the size of the tower segments to be produced, the reinforcing cages already have a considerable weight and, depending on the tower segment, sizable dimensions. A reinforcing cage has, for example, for the lowest, i.e., largest tower segment of a type E126 wind turbine from the ENERCON company, a diameter of approximately 14 m, a height of approximately 3.7 m and a weight of approximately 8.5 t. Because of its grid-like structure and the enormous dimensions, during manufacture reinforcing cages can only be handled with difficulty using conventional crane systems.
A gripping device for handling such reinforcing cages is known from DE 10 2012 221 453.
As well as handling the reinforcing cages, in the known manufacturing environments there is, however, a need to design the connection of the substantially vertical elements to the substantially horizontal ring elements of the reinforcing cages more efficiently and at the same time to be able to handle them using the known gripping device referred to above.